Abstract

The adaptation of death–feigning (thanatosis), a subject that has been overlooked in evolutionary biology, was inferred in a model prey–and–predator system. We studied phenotypic variation among individuals, fitness differences, and the inheritance of death–feigning behaviour in the red flour beetle, Tribolium castaneum (Herbst) (Coleoptera: Tenebrionidae). Two–way artificial selections for the duration of death–feigning, over 10 generations, showed a clear direct response in the trait and a correlated response in the frequency of death–feigning, thus indicating variation and inheritance of death–feigning behaviour. A comparison of the two selected strains with divergent frequencies of death–feigning showed a significant difference in the fitness for survival when a model predator, a female Adanson jumper spider, Hasarius adansoni Audouin (Araneomophae: Salticidae), was presented to the beetles. The frequency of predation was lower among beetles from strains selected for long–duration than among those for short–duration death–feigning. The results indicate the possibility of the evolution of death–feigning under natural selection.